1. Field of the Invention
The present invention relates to the field of a method for fabricating a heat pipe structure in a radiating plate , and more particularly, to a method for fabricating a monolithic heat transfer device having a heat pipe structure integrally formed within the heat transfer device. The heat transfer device in accordance with the present invention is monolithic and seamless, thus achieving low heat resistance and high heat transfer efficiency. The heat pipes are arranged in an orthogonal matrix manner.
2. Description of the Prior Art
Various heat pipe techniques have been applied on heat transfer devices for efficiently transferring heat generated from a heat source such as an integrated circuit. FIG. 1 shows a perspective view of a typical heat transfer device with a heat pipe. As shown in FIG. 1, the prior art heat transfer device generally includes a aluminum pad 7, a radiator 1 attached to the aluminum pad 7, and a plate 6 laterally fixed on the aluminum pad 7 and located near the radiator 1. The radiator 1 has a plurality radiating fins 11 . An adapting slot 12 is formed at a bottom portion of the radiator 1 for adapting a heat pipe 3. An askew groove 61 is formed in the plate 6. One end of the heat pipe 3 is inserted into the adapting slot 12 and the other end of the heat pipe 3 is fittingly wedged into the groove 61 in a slightly bent manner. In this way, heat is transferred from the plate 6 to the radiator 1 that is located near a fan (not shown) when in use. Solder paste 62 is used to fill gaps between the heat pipe 3 and the groove 61. FIG. 1A is a cross sectional view of heat pipe of FIG. 1. On interior surface of the heat pipe 3 there is provided a capillary structure 31. Working fluid 32 is enclosed in the heat pipe 3. Likewise, thermal grease 33 is used to fill gaps between the heat pipe 3 and the adapting slot 12.
However, the prior art heat transfer device of FIG. 1 encounters following problems:
1. It is troublesome for a manufacturer to form the adapting slot 12 of the radiator 1, and then insert the heat pipe 3 into the slot 12;
2. Heat conductive efficiency is affected since gaps may be formed, more or less, between the heat pipe 3 and the plate 6;
3. Quality of the heat pipe 3 is hardly controlled;
4. Since the heat pipe 3 is mounted on the aluminum pad 7 in a bent manner, portions of the capillary structure 31 may be damaged;
5. The aluminum pad 7 are formed from aluminum, heat pipe 3 are formed from copper and the solder paste 33 are formed from tin Aluminum,copper,and tinare different materials so heat conductive efficiency is thus reduced;
6. Although the gap between the heat pipe 3 and the plate 6 and the gap between the heat pipe 3 and the radiator 1 are both filled with thermal grease 33 and solder paste 62, rifts due to thermal expansion effect may be formed therein after long term use, thereby reducing the lifetime of the heat transfer device;
7. The prior art heat pipe 3 is subject to stresses that lead to cracking problems. In such case, the heat transfer device losses its heat transferring ability; and
8. Additional heat pipes are costly.
FIG. 2 is a cross sectional view showing another prior art heat transfer device utilizing a plate-type container. As shown in FIG. 2, the heat transfer device comprises a radiator 1 and a plate-type container 2 consisting of a top plate 21 and a bottom plate 22. The radiator 1 with a plurality of fins 11 is mounted onto the plate-type container 2 by means of solder paste 212. The bottom plate 22 is in contact with an object 4 to be cooled. The top plate 21 is combined with the bottom plate 22 to form a sealed space. A plurality of protuberances 211 are formed on a bottom surface of the top plate 21. Acapillary structure 221 is provided in the sealed space between the top plate 21 and the bottom plate 22. The sealed space is vacated and then injected with a working fluid (not shown).
Nevertheless, such configuration suffers from disadvantages such as high heat resistance between the radiator 1 and the plate-type container 2. Since the radiator 1 is mounted onto the plate-type container 2 by means of soldering, heat transfer efficiency is thus reduced. Further, the top plate 21, the bottom plate 22 and the protuberances 211 may be distorted or damaged when vacuating the sealed space defined by the top plate 21 and the bottom plate 22. The distortion of the bottom plate 22 may cause discontinuous and incomplete contact with the object 4 to be cooled.
From above, the disadvantages concerning the above-mentioned prior heat transfer devices may be summarized as follows:
1. The prior heat transfer devices are subject to distortion or cracking caused by negligent collision that leads to vacuum break of either the heat pipe or the plate-type container. In such case, the object to be cooled such as a CPU(central processing unit) may be burned out due to malfunction of the heat transfer device;
2. The prior heat transfer devices as depicted in FIG. 1 and FIG. 2 are complicated;
3. An optimal orthogonal arrangement of heat pipe cannot be achieved by the prior configuration as depicted in FIG. 1, since another heat pipe is required in a direction vertical to the heat pipe 3. Also, although the optimal orthogonal arrangement may be achieved by the prior structure depicted in FIG. 2, the protuberances 211 still suffer from distortion; and
4. The solder paste 62, thermal grease 33 and solder paste 212 are required in both prior heat transfer devices. However, the optimal coating thickness of the solder paste or thermal paste is hard to control. Besides, the solder paste or thermal paste may lead to cracking problem and seams or rifts may be observed after long-term use.
Consequently, there is a strong need to provide a heat transfer device and its fabrication method to solve the above-mentioned problems. The fabrication method according to this invention is simplified and suitable for industrial mass production.
It is a primary object of the present invention to provide a method for fabricating a heat pipe structure in a radiating plate. The heat transfer device in accordance with the present invention is monolithic and seamless, thus achieving low heat resistance and high heat transfer efficiency. The heat pipes are arranged in an orthogonal matrix manner. By virtue of the monolithic structure of the heat transfer device of this invention, structure strength is significantly improved and thus a substantially complete contact between an object to be cooled and the heat transfer device may be achieved. Heat generated from a heat source is transferred without passing through different medium of materials or any solder paste within the heat transfer device.
It is another object of the present invention to provide a method for fabricating a heat transfer device having advantages such as high yield, low weight, thin, and short fabrication time.
It is still another object of the present invention to provide a heat transfer device with a plurality of radiating fins and integral heat pipe structure to improve heat transfer efficiency.
It is still another object of the present invention to provide a method for fabricating a heat transfer device suitable for mounting on various heat transferring systems or heat dissipating modules.
According to the claimed invention, a method for fabricating a heat pipe structure in a radiating plate is provided. A tunneling means is used to form a plurality of radiating channels in the radiating plate. Each of the plurality of radiating channels has only opening. Then, only one of the openings of the radiating channels is not sealed, while sealing the other openings of the radiating channels. Working fluid is injected into the radiating channels via the reserved opening. Radiating channels is evacuated and the reserved opening is sealed.